Vibrating screening feeder and method of use

ABSTRACT

A vibrating screen feed conveying apparatus for conveying and separating sticky “moisture laden bulk solids” which are sticky and wet flowing onto a vibrating screening feeder and into a hopper. The apparatus includes a bed on which material is conveyed, a longitudinal counterbalance supported on a plurality of isolation springs, a plurality of inclined drive springs extending between the bed and the longitudinal counterbalance, and a plurality of stabilizers for controlling movement of the drive springs along their central axes. A plurality of vibratory motors, each having rotatable eccentric weights are attached to the rear end of the longitudinal counterbalance. The eccentric weights rotate in phase with one another to vibrate the bed at a vibration frequency.

CROSS REFERENCES TO RELATED APPLICATIONS

This is a Continuation application of U.S. application Ser. No.17/130,339 filed on Dec. 22, 2020 which is a Continuation of U.S. Ser.No. 15/741,655 filed on Jan. 3, 2018 now abandoned, which claimspriority from PCT/US2016/000056 filed on Jul. 5, 2016, all of which areincorporated by reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to the field of industrial vibratingscreens for separating small elements from large elements, such as inthe case of coal or stone.

BACKGROUND OF THE INVENTION

In the handling of particulate bulk material, there are numerous waysfor conveying such material and feeding it over an open end of theconveyor to a desired point of delivery. This invention is concernedwith a conveyor or feeder vibrated as a free mass, i.e., the trough orconveyor is suitably isolated from the ground so that it may be vibratedin response to an oscillating force, as distinguished from a mass whichis positively connected to the exciting force, as, for example, bydriving the conveyor through an arm rigidly connected to a fixed strokeeccentric drive.

Vibrating screens are in use in numerous industrial situations where thenecessary separation of dust and fine particles of a given product isnecessary. For example, electrical utility companies burn coal, whichmust be delivered to the boilers in almost powdered form and screeningof the coal aggregate is necessary in very great volumes.

Conventional mechanical means operate by varying the frequency or thestroke of the feeder. An exception to mechanical means for adjustingrates of feed is in the case of an electromagnetic drive for a feeder,in which case the frequency or the voltage of the applied pulsatingcurrent applied to the electromagnetic drive is varied. However, in thistype of device the vibrations per minute used are generally above 1800cycles per minute and have relatively short strokes with the result thatsuch feeders are limited to bulk materials of the more free-flowing typeas distinguished from those which are characterized as damp or viscous.

Mechanical means may include a variable rate spring device such as anair bag interposed in the drive with the pressure in the air bag beingadjustable to effect the change of spring rate, or some form ofmechanical adjustment of the drive motors angularity or positionrelative to the pan. There have been many attempts, in vibratoryfeeders, to utilize some form of adjustable feed rate control usingelectrical phenomena, but to date none of these have been successful fora number of reasons. The electromagnetic type vibrators have high energylosses and are restricted to essentially high frequency and short strokecombinations. Low frequency, long stroke devices have been conceivedthat utilize adjustable frequency A.C. drives, multi-speed, and/ormulti-winding A.C. motors, or adjustable voltage D.C. drives which havenot met with success because of high initial cost, and the cost ofmaintenance due to brush wear, commutator problems and the like.

Induced conveying improves material handling in applications wheredifferent kinds of solid fuels are used to produce heat in a boiler witha vibrating stoker grate that burns it. The vibratory feeders andscreens induce the fuel's movement instead of forcing it. This avoidssqueezing and bunching the fuel. The Particles remain loose whichfacilitates more efficient burning. Some power plant boilers are firedby fuels such as coal meeting a demanding specification wherein the fuelmet the designation of “steam coal” having a particle size, density, andmoisture content specified for efficient combustion.

When fuel is scarce because of shortages uncleaned run-of mine (ROM)coal and the waste coals such as culm, gob, silt, or high moisture “wet”coal are burned, especially in countries having economic difficulties.The biomass fuels of bagasse, wood waste such as bark, chips, shavings,and sawdust fuel is used to fire boilers. Refuse derived fuels (RDF)which is shredded municipal waster and whole or shredded rubber triescan also be sources of fuel. Density and moisture content are difficultto control. The induced vertical flow and induced conveyance flowprovided by vibrating feeders, screens, and conveyors are used becausethese fuels are usually obstinate to flow from storage.

Generally, a vibrating screen is fixedly mounted in a screen housingwith supporting frame work. The screen housing is then supported above afixed base by springs or rotatable arms. The screen housing is caused tovibrate by some sort of drive which shakes the housing. Some drives arefixed to the base and connected by a crank journal to the vibratingscreen housing. The prior art illustration shown in FIG. 1 shows a fixedbase member 102, a motor 112 and a crank journal 114 driving a vibratingscreen housing 108 which is movable relative to the fixed base 102 aboutrotating arms 104 with damper springs 20. Other drives consist of amotor fixed to the vibrating screen housing driving eccentric weightswhich then cause the screen housing to vibrate. These units haveinherent disadvantages such as difficulty of changing or repairing motordrives and large energy consumption.

In the vibratory industry, vibratory conveying apparatus such asvibrating feeders, vibrating conveyors, vibrating screens, vibratingheat transferring fluidized beds, attrition mills, and the like, wereall powered by a well-known and popular driving method called the“Single Input” or “Brute Force” type of drive. A single pair of rotatingeccentric weights is the sole source of the input power in this kind ofdrive. Being installed directly across from one another, a single pairof eccentric weights rotating in opposite directions vibrate thevibratory conveying apparatus with a linear or “back and forth”,straight line motion. As the load carrying capability of the conveyingapparatus increased over the years, the weight of the rotating eccentricweights also necessarily increased in size, and the horsepower demand ofthe electric motor utilized to rotate the eccentric weights increasedaccordingly.

When more input power is needed to move heavier loads along the lengthof the conveying trough, more rotating eccentric weight force andhorsepower are needed. Consequently, the rotatable eccentric weightsbecome larger and heavier and have a greater force output. Likewise, theelectrical windings in the vibratory motor increase in size to producemore horsepower. This increase in eccentric weight force output and therespective vibratory motor horsepower has approached the point that thevibratory motors are presently as large as practical to manufacture orto utilize on a vibratory conveying type of apparatus.

Electric motor applications attempt to match motor torque operatingcharacteristics with load torque characteristics. Conventional electricmotor applications teach that an AC. squirrel cage motor is not to beused for adjustable speed drive, because the load torque requirementsare such that when an attempt is made to substantially alter speedthrough change in voltage, the motor is overloaded and will burn out,except in the case when the motor drives a fan or a pump which is usedin moving a fluid, wherein the load torque requirements are consistentwith the thermal capability of a squirrel cage motor.

In the present invention it is possible to use an A.C. squirrel cagemotor and adjust the voltage thereon to vary the feed rate of thevibratory system is because the vibratory system is of the free mass,natural frequency type, that is, the motor exciter drive is a part of anatural frequency vibratory system and the vibratory system is isolatedfrom ground, as distinguished from a vibratory system which is drivenpositively from a fixed stroke rotary eccentric member as best describedby Applicant prior U.S. Pat. No. 3,251,457 for a Method and Apparatusfor Driving Vibratory Devices which issued in 1965 and is incorporatedby reference herein in its entirety.

As the system operates below natural frequency, the mass inertia vectoris diminished, the spring effect is diminished, the damping losses arediminished, and the applied force is subdivided into a horizontal andvertical component, with the horizontal component matching the dampinglosses, and the vertical component acting in opposition to the springeffect. This in itself creates a mechanical impedance on the motorresulting in the stroke of the feeder being diminished, and explains whythe current drawn by the motor, which is proportional to the dampinglosses, diminishes as one moves below natural frequency. Therefore, anAC. squirrel cage motor may be used effectively to change the speed ofthe motor and a natural frequency resulting in a free mass vibratorysystem.

Watts, volts, amperes, and stroke characteristics vary exponentially inrelation to speed, and that a small change in speed causes a markedchange in feed rate, current, and watts, which explains why the feedrate can be changed in this manner without burning up the motor. Theload torque characteristics of the motor are being matched with the loadtorque demands of the vibratory mass system.

It is the objective of this invention to operate as near the peak of thecurve as is possible for maximum feed and normal load conditions. As apractical matter, the spring rates are chosen for a load condition tohave the system operate when the vibrating screening feeder is carryinga normal load. As voltage is reduced on the motor to move from maximumfeed rate to a lesser feed rate, the frequency and′ stroke are bothreduced until a zero feed rate is approached.

It is contemplated that a fixed rate spring will be used for tuning thevibratory mass to the frequency of the oscillatory drive. It is possiblethat a variable rate spring might in some instances be used toapproximate the natural frequency of the system. The control offrequency and stroke would be accomplished by dropping the voltage onthe AC squirrel cage motor.

An auto-transformer has shown in prior art FIG. 19 provides a way toadjust the voltage on the AC motor. Other ways in which the voltage maybe regulated is, for example, by the use of solid state type controlincluding a gating transistor.

Another common problem with vibrating screens occurs when screens becomejammed or clogged with aggregate material. This clogging slows or stopsthroughput causing costly shutdown for screen cleaning and unclogging.The instant invention includes a pulsing solution to dislodgecontaminants from the screens.

SUMMARY OF THE INVENTION

A continuous, steady flow of the supply of the incoming bulk solid suchas coal, ore, wood waste, or the like is required as feed material foroptimal control and screening performance of the feeding and screeningsystem. It is recommended that the vibrating screening feeder beinstalled under the outlet of a storage bin or silo or surge bin. Theoutlet of the steady feed source must be interfaced with the vibratingscreening feeder inlet chute that connects to the feed bin. The chutetypically includes a baffle of 30 to 60 degrees and preferably about 45degrees to help convert the vertical feed flow into the inlet to ahorizontal or near horizontal flow and spread across the full width ofthe vibrating screen feeder feed plate. The screen media is usuallywoven wire of perforated plate with longitudinal side clamps, flapplastic squares or any standard screen media. Three screening decks aretypically used in the apparatus; however, it is contemplated thatadditional decks may be added. The passed unders (under sized particles)collecting pan is disposed beneath the screening plates and extends thefull width and length of the screen for collecting and conveying all ofthe passed unders to an outlet located near to the end of the screen.The collecting pan includes an outlet for discharging the passed underslocated near the end of the screens and can be full width or converging.The means for powering the vibrating screening feeder is accomplished byan AC motor rotating unbalanced eccentric weights combined withsub-resonant tuned steel coil drive springs which are attached to theend of a longitudinal counterbalanced support base which is alongitudinal structure which can be cut into sections that are boltedtogether if necessary. The instant invention concentrates and nests thesteel drive coils in selected positions or locations connecting thescreening unit to the longitudinal counterbalance support base.

A vibrating conveyor screening and feeding process for conveyingmaterials includes a bed having an inlet end and an outlet end on whichmaterial is adapted to be conveyed in a direction. A plurality of drivesprings each have a first end attached to the bed and a second endattached to a support. Each drive spring is adapted to compress andextend along a line of stroke. A plurality of stabilizers attaches tothe bed, each one being more rigid in a direction transverse to the lineof stroke than the stabilizer is rigid in the direction of the line ofstroke. A first vibratory motor has a first rotatable eccentric weightadapted to state about a first axis. A second vibratory motor has asecond rotatable eccentric weight adapted to rotate about a second axis.A third vibratory motor has a third rotatable eccentric weight adaptedto rotate about a third axis. A fourth vibratory motor has a fourtheccentric weight adapted to rotate about a fourth axis. The first andsecond axis are located substantially in a first plane and the third andfourth axis are located substantially in a second plane. The secondplane is non-coplanar with the first plane and the first and second axisare spaced apart from the third and fourth axis along the direction thematerial is conveyed. The eccentric weights are free-wheeling withrespect to one another. The vibratory motor is adapted to operate atsubstantially the same operating speed and to provide an output forcegenerally perpendicular to its axis of rotation. The rotatable eccentricweights are adapted to accumulatively synchronize with one anotherwithout being rotationally coupled to one another such that the combinedresulting output force of the first pair of rotatable eccentric weightsis generally parallel to the line of stroke and the combined resultingoutput force of the second pair of rotatable eccentric weights isgenerally parallel to the line of stroke. The vibratory motors operateto rotate the eccentric weights, such that the rotating eccentricweights accumulatively synchronize and accumulatively add their outputforces and their respective power outputs and thereby vibrate the bedalong the line of stroke at a vibration frequency. The vibratory motorsoperate at substantially the same selected operating speed whichapproaches being equal to, or is less than, the natural frequency of thedrive springs which are vibrating the bed.

A novel feature of the instant invention is based on the electricalcontrol enabling a full zero to maximum output adjustment by means ofadding a standard variable frequency (VFD) combined with adjustabletimers so that a vibratory stroke required screening has an automaticcapability of a momentary “pulsing” to 60 hertz (or higher) for a brieftime of usually 3 to 5 seconds, which generates a vigorous vibratoryaction “spurt” or “pulse” to the entire screening body similar to a dogshaking off water. The pulsing action is usually automatically repeatedto keep the screen media clear of “pegging” or being blinded by lumps orparticles stuck in the openings or to break free accumulated layers ofadhesive and cohesive particles that try to stick or adhere to thesurface of the screening media and the passed unders collecting panbelow it.

Another novel feature of the present invention is the feedback controloperation of the vibrating screening feed based upon the throughputcapacity of the equipment it is feeding. For instance, if feeding a rockcrusher, a standard 4 to 20 ma direct current (D.C.) signal can be usedto automatically control the vibrating screening feeder's variablefrequency (VFD) control of the screening feeder. The closed loop of thecontrol circuit monitors the amps drawn by the rock crusher to controlthe feed rate of the vibrating screening feeder by increasing ordecreasing the output of the fed from the vibrating screening feeder.Thus, the amps pulled by the equipment being fed will control the rateof feed. The variation form zero to maximum TPH output and the repeated“pulsing” of making the motor with eccentric weights to go faster andthen return to a slower, steady speed is accomplished with the 3 phasealternating current (A.C.) squirrel cage motor.

Another feature facilitating processing of sticky feed material is across bar with water spray nozzles which can optionally be used whenadhesive and cohesive bulk solids are being screened to clean thesticking particles to the screening surface of the collecting panunderneath.

Use of stainless steel or other alloys which tend to resist stickyresidues are also useful to eliminate sticky residue and agglomerates.Coatings such as TEFLON may also be used to treat the surface ofequipment to resist sticky residue.

The vibrating screening feeder is dust tight having a bolted top coverwith quick opening view ports add to the screen body. Enclosed verticalchutes are added to the discharge end. Flexible connections also sealthe inlet and the outlets.

In accordance with features of the invention, the vibration driveisolation assembly includes a longitudinally extending longitudinalcounterbalance member. A plurality of drive springs are supported by thelongitudinal counterbalance member. The drive springs are distributedacross the width and the length of the enclosed screening unit. At leastone vibratory motor or mechanism is installed on the proximate end ofthe longitudinal counterbalance member. A plurality of isolation springssupport the longitudinal counterbalance member.

Induced conveying is accomplished by imparting a proper stroke at theneeded frequency to move the load. The result is a conveying motion thatis induced instead of being forced. It can be a very gentle type ofmovement or when necessary, a very sharp, reacting type of vibrationwhich can be produced by using an appropriate stroke angle. A helical orelliptical stroke pattern will convey the material in a circular pathresulting in a backspin on the particle. A linear stroke is the mostefficient one to use for unidirectional movement which moves thematerial in a straight line. The vibratory action does most of the work.When vibrated, the inner particle friction of the moved material isreduced.

A particle can be vibrated and conveyed over a hard surface by means ofa series of repetitive “hops”. Each “hop” is a cycle. The distancehopped is directly related to the unit's stroke length and the angle atwhich it is applied. The “hops” per unit of time is the operatingfrequency which is usually expressed in “cycles per minute” or (CPM).

An alternative vibratory motor embodiment suitable as a drive means forthe vibratory screening feeder utilizes a double extended shaft witheccentric weights installed on both ends of the shaft and arecumulatively considered as a single rotatable eccentric weight.Vibratory motors equipped with shaft mounted eccentric weights will beemphasized herein, but other jack shaft driven combinations can also beused such as v-belts and the like. In either instance, the pair ofrotatable eccentric weights are installed on and become an integral partof the conveying assembly.

It is an object of this invention to provide a vibrating screen forseparating of at least two particle sizes of aggregate in a continuousflow process.

It is an object of this invention to provide a vibrating screen forseparating of at least two particle sizes of aggregate in a continuousflow process which has a low horsepower to tonnage throughput ratio ascompared to other separation processes.

It is an object of this invention to provide a vibrating screen whichincludes a periodic cleaning and unclogging of the screens wherein thespeed of the drive motors is periodically and briefly changed by anominal amount for a short time to dislodge blockages.

It is an object of this invention to provide a vibrating screen whichprovides motors located in an easy to maintain location at one end ofthe vibrating screen unit.

It is an object of the present invention to provide an electricallycontrolled, a vibratory drive powered by electric motors or highfrequency electromagnets that are combined with steel coil springs thatare sub-resonant tuned (enabling drive springs to drive harder underloaded conditions), to provide a vibrating screen for unidirectionalmaterial movement whereby the vibratory drive is the prime mover of thematerial (induced conveying) as opposed to conventional vibratory feedswhich depend upon the force of gravity (induced vertical flow) as theprime mover of the material.

It is an object of the present invention to convey and screen materialin response to applied vibratory action via a free force vibratory inputcombined with subresonant tuned springs to reduce interparticle frictionand stratify the material into layers by particle size.

It is an object of the present invention to utilize the principle ofresonance or natural frequency and to subresonant tune the drive springsto produce more under load whereby the machine' operating frequency isalways kept below or under the resonant point of all the drive springs.

It is an object of the present invention to provide a vibratory feederand screen apparatus whereby the dynamic acceleration is the same inboth directions of the back and forth movement of its vibratory motionversus a reciprocating motion that moves forward slowly and thenaccelerates rapidly on its return stroke.

It is an object of the present invention to provide a vibratory feedercapable of screening wet bulk solids that are adhesive and cohesive.

It is an object of the present invention to provide a vibrating feederand vibrating screen assembly which can tolerate variation in moisturecontent.

It is an object of the present invention to incorporate a drive systemfor a vibratory feeder and conveyor powered by one or more electricmotors with input power provided by eccentric weights rotated by eachmotor, a linear stroke pattern, a wide range of operating frequencies,electrically adjustable output with zero to maximum output by variablevoltage, with the stroke and frequency simultaneously changed,subresonant operational tuning, longitudinal counterbalanced vibratoryforce isolation, and capable of smooth repetitive starts and stops.

It is an object of the present invention to provide a drive systemhaving three primary components comprising a steel coil drive springthat produces the portion of the load that opposes the vibratory motion,a plurality of flat bar stabilizers guide the motion, and the motorproduces the remaining portion of the load that resists it.

It is an object of the present invention to provide an energy efficientdrive system for the vibrating feeder and screen apparatus.

It is an object of the present invention to provide a screening deckfor: cleaning unit pieces by removing clinging particles such as adheredsand or trimming edges; for washing by mounting rows of liquid spraysdirectly over the screen medium, a bulk solid or a unit piece so theliquid spray such as water, oil, surfactant, defactant, or other washingaction; sizing to separate flakes and sizes; scalping to remove oversizeparticles; removing undersize particles; grading; de-liquefying;de-sliming by washing the clinging fines from freshly crushed lumpymaterials; rinsing; de-watering; and draining.

It is an object of the present invention to include an underside pan forrecollecting all the passed unders.

It is an object of the present invention to utilize conveying surfacesdynamically counterbalanced and isolated with isolation springs toreduce motor power consumption by 50 to 70 percent compared toconventional motors achieving the same performance.

It is an object of the present invention to utilize multiple small lowHP motors with synchronized rotating eccentric weights in place oflarger higher HP motors.

It is an object of the present invention to provide a “dust-tight”vibrating screen design.

It is an object of the present invention to provide an unidirectionalinduced conveying apparatus counterbalanced with isolator springs tosupport it.

It is another object of the present invention to provide an extremelysimple and practical way to adjust frequency and stroke, in the drivefor vibrating devices combined with mechanical impedances which arepurposely built into the vibrating mass system.

A further objective of the invention is to provide an electric drive forvibratory equipment which lends itself to simplified remote control forchanging the frequency and the stroke of the vibratory equipment.

A still further object of the invention is to make use of an A.C.squirrel cage induction motor which is well known to have ruggedperformance characteristics, low maintenance costs and low initial costsas compared to other electrical motors which are capable of adjustablespeeds.

Other objects, features, and advantages of the invention will beapparent with the following detailed description taken in conjunctionwith the accompanying drawings showing a preferred embodiment of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had uponreference to the following description in conjunction with theaccompanying drawings in which like numerals refer to like partsthroughout the views wherein:

FIG. 1 is a side view of a prior art vibrating conveyor showing a fixedbase member, a motor and a crank journal driving a vibrating screenhousing which is movable relative to the fixed base about rotating armswith damper springs;

FIG. 2 is a side elevational view of the vibrating screening feeder unitillustrating natural frequency vibrating screening feeder in which theexciter motor is suspended from the vibratory mass system and acts inparallel with the drive springs which are selected to give the systemnatural frequency characteristics;

FIG. 3 is a view of a section of the vibrating screening feeder showingthe screening unit connecting to drive springs mounted on bracketssupported by the longitudinal counterbalance support base;

FIG. 4 is an end view of the vibrating screening feeder showing thescreening unit connecting to a plurality of drive springs mounted in arow across the width of the screening unit and longitudinalcounterbalance support base which is supported by a plurality ofhorizontal coil steel isolation springs supporting the longitudinalcounterbalance support base on a base and showing a plurality of motorsmounting on the end of the longitudinal counterbalance support base;

FIG. 5 is a perspective view of the vibrating screening feeder unit ofthe present invention showing the screening unit side walls and panhaving brackets connecting to a plurality of drive springs mounted in arow across the width of the screening unit and longitudinalcounterbalance support base;

FIG. 6 is an elevated perspective view of the vibrating screening feederunit showing the discharge chutes extending from the rear end of thepresent invention;

FIG. 7 shows that when the drive springs 20 are expanded, the rockersprings 24 are flexed upward.

FIG. 8 shows that when the drive springs are compressed, the rockersprings 24 are flexed downward.

FIG. 9 shows a vibratory motor with rotatable eccentric weights;

FIG. 10 shows the vibratory motor of FIG. 9 including extra weightsadded to the shaft;

FIG. 11 is an end view of a vibrating screening feeder unit showing thestorage bin positioned above the vibrating screening feeder andconnecting the bin outlet to the feeder inlet interfacing chute;

FIG. 12 is a side view of the vibratory screening feeder showing a chuteconnecting the bin to the feeder inlet and the screening unit supportedby the longitudinal counterbalance on drive springs and the longitudinalcounterbalance supported on the base with steel coil isolation springs;

FIG. 13 is an end view of the vibrating screening feeder showing themotors attaching to the end of the longitudinal counterbalance, a row ofisolation springs supporting the screening unit above the longitudinalcounterbalance and the drive springs on the outside of the row extendingacross the screening unit supported by the longitudinal counterbalance;

FIG. 14 is an elevated side view of the vibratory screening feedershowing a chute connecting the bin to the feeder inlet and the screeningunit supported by the longitudinal counterbalance on drive springs andthe longitudinal counterbalance supported on the base with steel coilisolation springs wherein the longitudinal counterbalance is angleddownward at a 15 degree angle with respect to the base;

FIG. 15 is an elevated side view of the vibratory screening feeder ofFIG. 16 showing a chute connecting the bin to the feeder inlet and thescreening unit supported by the longitudinal counterbalance on drivesprings and the longitudinal counterbalance supported on the base withsteel coil isolation springs wherein the longitudinal counterbalance isangled downward at a 15 degree angle with respect to the base andshowing the optional water spray bars and discharge connection to acrusher;

FIG. 16 is an end view showing the connection of the vibrating screeningfeeder to the crusher and the discharge chute;

FIG. 17 is a side elevational view showing the drive of this inventionapplied to a natural frequency vibratory feeder where the springs are inseries with the motor drive.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the FIGS. 1-17 , a vibrating screening feeder system 1includes a vibratory storage bin 8 feeding a vibrating screening feederunit 10 feeding and crusher 70 for oversized material. The intermediatestorage bin 8 is positioned above the vibrating screening feeder 10connecting the bin outlet 102 to the feeder inlet interfacing chute 104.The size of the bin 8 is determined by the throughput to maintain amaximum feed rate to the vibratory screening feeder 10 and ensure anappropriate amount of storage to enable it to continuously operate atits rated TPH (ton per hour) capacity. The bin's outlet 102 ispositioned close to the feeder inlet 103 separated by the feed plate105. Preferably the bin 8 is a vibratory bin or hopper having thecapability to shake accumulations or bridging particles from thesidewalls to effect a smooth flow of feed to the vibratory screeningconveyor 10. The following U.S. Patents are incorporated by referenceherein are some of the vibratory hoppers which may be useful forutilization with the present invention: U.S. Pat. Nos. 3,261,592;3,257,040; 5,046,643; 4,960,229; 3,735,963; 4,744,893; 4,899,669; and4,844,289.

As shown in FIGS. 2, and 11 , a chute 104 or stove pipe can be used toconnect the bin to the feeder inlet 104. On “start-up” the top sectionor cover is temporally removed to permit the adjustment of the “matdepth” flowing into the vibrating screening feeder 10. When adjustedproperly, full width spreading is obtained and the cover 56 isreinstalled over the unit. Also shown are the horizontal coil steelisolation support springs 22 which are nested in sets and mounted tosupport members 23 extending across the width of the conveyor. Theisolation springs 22 rest on a base, floor or other immobile supportsurface. A alternate motor 50 is shown mounted to the longitudinalcounterbalance 26.

FIG. 13 is an end view of the vibrating screening feeder showing themotors attaching to the end of the longitudinal counterbalance, a row ofisolation springs 22 supporting the screening unit above thelongitudinal counterbalance and the drive springs 20 on the outside ofthe row extending across the screening unit supported by thelongitudinal counterbalance. The vibrating screening feeder 10 shownincludes 200 drive springs 20 are arranged in sets of two rows eachextending across the width of the conveyor attaching to the conveyor bedframe or integral body/frame support members 18 supported at a 45 degreeangle by brackets 19 mounted on the top of the longitudinalcounterbalance support base 26. Each drive spring or coil is equivalentto ½ HP. Thus, 200 drive springs provide the equivalent of 100 HP ofdriving force to the vibrating screening feeder 10.

As shown in FIG. 14 , the vibratory screening feeder shows a chuteconnecting the bin to the feeder inlet and the screening unit supportedby the longitudinal counterbalance on drive springs and the longitudinalcounterbalance supported on the base with steel coil isolation springswherein the longitudinal counterbalance is angled downward at a 15degree angle with respect to the base.

FIG. 15 is an elevated side view of the vibratory screening feeder ofFIG. 14 showing a chute 104 connecting the bin 8 to the feeder inlet andthe screening unit 10 supported by the longitudinal counterbalance ondrive springs 20 and the longitudinal counterbalance supported on thebase with steel coil isolation springs 22 wherein the longitudinalcounterbalance is angled downward at a 15 degree angle with respect tothe base and showing the optional 450 gallon per minute (GPM) waterspray bars 52 and valve 54 and discharge connection 44 to a crusher 70for minus 7 millimeter material. FIG. 16 is an end view showing theconnection of the vibrating screening feeder to the crusher 70 and thedischarge chute 44.

The vibrating screening feeder 10 consists or comprises a trough or pandefined by a bottom floor 11, side walls 12 and 13, and a rear end wall14, with the forward end wall 15 including chutes 40, 42, and 44 influid engagement with downstream processing equipment. The processedfeed material is delivered to a desired conveyor or process equipmentpoint at some selected rate of speed. The vibrating screening unit 10 ismounted on support members 18 which are carried at selected points atthe front and rear portions of the a vibrating screening feeder 10mounted beneath the trough, bed, or pan 11.

The drive springs 20 are preferably selected with K factors, that is,spring rates which are appropriately related to the frequency of themotor drive, the mass of the motor drive component, and the total massof the driven vibratory system, so that under normal synchronous speedof the drive motor, the springs 20 will be at or near natural frequencywith the system. For ideal operation, the vibratory system with itsexciter drive is designed to operate at, as close to, the naturalfrequency of the system as illustrated by the stroke-frequency curve ofFIG. 7 of U.S. Pat. No. 4,015,705 wherein the natural frequency is atthe peak of the curve.

It will be understood that the drive springs 20 are also designed sothat lateral forces transverse to the longitudinal axis of the vibratingscreening feeder 10 are absorbed by the lateral deflections of thesprings 20. Of course, if desired dual motors having the samecharacteristics as the motor 30, except for being each one-half thehorsepower of the single motor, may be used in place of the single motor30, in which case they are driven in opposite directions and have theirmotor housings rigidly joined together in a manner well known in the artso as to cause the rotating weights to phase together and cancel out thelateral forces while producing a resultant linear stroke.

A motor 30 for vibrating the vibrating screening feeder 10 at a selectedfrequency and stroke for moving particulate material on the pan 11toward the discharge end 14 of the feeder. The motor drive in thepresent invention is capable of adjusting the rate of feed by varyingthe frequency and the stroke of the vibratory system.

An unexpected surprising and unique relationship exists between thecharacteristics of the vibratory system and the driving motor, wherebyit is possible to vary not only the frequency, but also tosimultaneously vary the stroke of a natural frequency vibrating feederor similar vibratory system merely by changing the voltage on the A.C.motor 30. An A.C. squirrel cage motor has always been thought of asessentially a constant speed motor (except, of course, a multi speed ormulti-winding A.C. motor) one which could not have its speed effectivelyvaried by voltage control. The variable load requirements of a freemass, natural frequency, vibratory system in relation to speed aresimilar to those of a fan or a fluid pump and that it is possible to usevariations in the voltage applied to the A.C. squirrel cage motor as aneffective means for controlling the feeding rate of this type ofvibratory system, and that, surprisingly, this can be accomplishedwithout motor overload.

The ability to control feeder rate merely by voltage control lendsitself to the remote control of systems of this type, and is far moreconvenient than attempting to adjust or vary the rate of theforce-transmitting spring units interposed between the motor 30 and thevibrating screening feeder 10.

The motor drive 30 comprises a single alternating current squirrel cageinduction motor which is supported on the end of the longitudinalcounterbalance 26 from a motor mount bracket rigidly secured thereto.The motor has a squirrel cage rotor, and is thereby characterized as onewhich does not have brushes. For convenience the type of A.C. motor willhereinafter be referred to simply, as an A.C. squirrel cage motor, andis to be distinguished from a variable speed A.C. motor having multiplewindings or multipoles for speed control.

As shown best in FIGS. 9-10 , at each end of the shaft 33 of the motor30 an eccentric weight 52 is mounted, and usually these weights arefixed to the shaft in parallel relationship, although in some instances,it may be desirable to vary their angular relative positions to achieveadjustment of the effective eccentric mass operating on the vibratorysystem, or adjusting weights 54 may be added to or subtracted from theeccentric weights, as required. Shrouds cover the ends of the motor toprotect personnel from the revolving eccentric masses.

The motor 30 is supported on the longitudinal counterbalance in such amanner that the exciting oscillatory force supplied by the eccentricallyweighted motors is applied to the vibratory conveyor screening unit 9along a fixed angle of attack. This angle of attack is ordinarily on theorder of from 20 to 40 degrees, and it will be seen that as anoscillating force is applied to the vibrating screen 9 along this axis,the particulate on the vibrating screen 9 is caused to move toward theopen end of the vibrating screen 9 by what might be termed a hoppingaction. As the frequency of the oscillating force is reduced and/or asthe stroke is reduced, the rate of feed is correspondingly reduced andit is desirable to have this rate of feed variable between zero, orsubstantially zero, and the maximum rate of feed.

It is an accepted fact in the natural frequency vibrating system field(as for example in the type of feeder shown in Klemencik U.S. Pat. No.2,725,984) that one can normally determine whether the system isoperating in natural frequency by checking the current draw on themotor, because, when the system is operating at true natural frequency,the current draw is at a minimum. Conversely, to the extent that asystem of this type is not operating at natural frequency, the powerrequirements go up, and this is reflected in increased current draw,regardless of whether one is operating above or below the point ofnatural frequency. Contrary to conventional teachings, when the presentinvention is operating in natural frequency, the current drawn by themotor is at its maximum, and, as the frequency (i.e. speed) of the motoris changed by dropping the voltage, the current decreases. As one movesbelow natural frequency with the system the current going through themotor drops rather than rises, as might normally be expected. It ispossible to effectively vary the feed rate of a vibratory conveying orfeeding system from-substantially zero to its maximum feed rate, merelyby adjusting the voltage of an A.C. squirrel cage motor. This of coursecan conveniently be done with an auto transformer, such as shown in FIG.17 .

The vibrating screening feeder is adapted to be driven by a plurality ofaccumulatively phased pairs of free-wheeling rotatable eccentricweights. The accumulative force output produced by the rotatingeccentric weights will be a unified amount equal to the sum of all themultiple pairs of eccentric weights. The respective power outputs of themotors turning these eccentric weights will also accumulatively add.This wanted “phasing” of multiple pairs of rotating eccentric weightswill only occur when used in conjunction with properly stabilized,sub-resonant tuned, stiff drive springs.

The accumulative phasing of a plurality of pairs of rotating eccentricweights is applicable to vibratory conveyors of the non-balanced type,which must be rigidly fixed to their support structure. It is alsoapplicable to vibratory conveying machines that are dynamicallycounterbalanced and provided with isolation springs. The longitudinalcounterbalance can be one single longitudinal assembly, or thelongitudinal counterbalance can be sectionalized in a plurality ofsections as shown in Dumbaugh U.S. Pat. No. 4,149,627. It is importantto note the vibrating screen 9 must employ the sub-resonant tunedsprings kind of vibratory drive configuration that is properlystabilized for this wanted multiple phasing of a plurality of pairs ofrotatable eccentric weights to occur.

The multiple pairs of rotatable eccentric weights are installed on andbecome an integral part of the conveying trough assembly of theconveying apparatus when the vibratory conveying apparatus is the“non-balanced” type. This means its longitudinal counterbalance frame isrigidly “fixed” to a robust stationary foundation. Conversely, when thevibratory conveyor is “dynamically counterbalanced”, the pair ofrotatable eccentric weights can be installed on either the conveyingtrough or on a counterbalancing member. When the conveying apparatus islongitudinal counterbalanced, the pair of rotatable eccentric weightsare almost always installed on the counterbalancing member.

Method of Use:

A continuous, steady flow of the supply of the incoming bulk solid suchas coal, ore, wood waste, or the like is required as feed material foroptimal control and screening performance of the feeding and screeningsystem. It is recommended that the vibrating screening feeder 10 beinstalled under the outlet of a storage bin or silo or surge bin 8. Theoutlet 102 of the steady feed source must be interfaced with thevibrating screening feeder inlet chute 104 that connects to the feed bin8. The chute typically includes a baffle of 30 to 60 degrees andpreferably about 45 degrees to help convert the vertical feed flow intothe inlet to a horizontal or near horizontal flow and spread across thefull width of the vibrating screen feeder feed plate 17.

The screen media 53 is usually woven wire or a perforated plate withlongitudinal side clamps, flap plastic squares or any standard screenmedia. Three screening decks, a (top deck 50, a middle deck 55, and abottom deck 58), and a bottom trough or pan 11 are typically used in thevibrating screening feeder 10; however, it is contemplated thatadditional decks may be added. The passed “unders” (under sizedparticles) collecting pan 11 is disposed beneath the screening platesand extends the full width and length of the screen for collecting andconveying all of the passed “unders” to an outlet located near to theend of the screen. The collecting pan 11 includes an outlet 44 fordischarging the “passed unders” located near the end of the screens andcan be full width or converging. The means for powering the vibratingscreening feeder is accomplished by motorized an AC motor rotatingunbalanced eccentric weights combined with sub-resonant tuned steel coildrive springs which are attached to the end of a counterbalanced supportbase which is a longitudinal structure which can be cut into sectionsthat are bolted together if necessary. The instant inventionconcentrates and nests the steel drive coils 20 in rows at selectedpositions or locations connecting the screening unit to the longitudinalcounterbalance support base 26.

The electrical control enables a full zero to maximum output adjustmentby means of adding a standard variable frequency (VFD) combined withadjustable timers so that a vibratory stroke of about 2 Gees for therequire screening (50 Hz at for about 25 seconds) has an automaticcapability of a momentary “pulsing” to (60 hertz (or higher) for a brieftime of usually 3 to 5 seconds), which generates a ver vigorousvibratory action “spurt” or “pulse” to the entire screening body similarto a dog shaking off water. The novel pulsing action is usuallyautomatically repeated to keep the screen media clear of “pegging” orbeing blinded by lumps or particles) stuck in the openings) or to breakfree accumulated layers of adhesive and cohesive particles that try to“stick” or adhere to the surface of the screening media and the passed“unders” collecting pan 11 below it.

A novel feature of the present invention is the control of the vibratingscreening feed by the equipment it is feeding. For instance, if feedinga rock crusher 70, a standard 4 to 20 ma D.C. signal automaticallycontrols the vibrating screening feeder's variable frequency (VFD)control of the vibrating screening feeder 10. The closed loop of thecontrol circuit comprises or consists of monitoring the amps drawn bythe rock crusher to control the feed rate of the vibrating screeningfeeder by increasing or decreasing the output of the fed from thevibrating screen. Thus, the amps pulled by the equipment being fed willcontrol the rate of feed. The variation form zero to maximum TPH outputand the repeated “pulsing” of making the motor with eccentric weights togo faster and then return to a slower, steady speed is accomplished withthe 3 phase A.C. squirrel cage motor.

More particularly, there is provided a vibrating screen unit 9comprising, consisting of, or consisting essentially of a generallyrectangular vibrating screen housing 79 supported by a fixed base 4defining a longitudinal counterbalance 26 by a plurality of upwardextending isolation support coil springs 22 fixedly attaching to a topsurface of the longitudinal counterbalance 26 and fixedly attached to abottom surface of the generally rectangular frame 8. The intermediateframe 8 has triangular shaped support members 18 defining alternatinglarge and small triangular abutments extending upward therefrom. Thelarge triangular abutments have a first side forming about a forty-fivedegree angle with a top surface of the longitudinal counterbalance 26.The first side of the large triangular abutment 18 have a drive coilspring 20 extending upward therefrom at about a forty-five degree anglewith a top surface of the longitudinal counterbalance 26. The smalltriangular abutment has two spaced apart leaf spring rockers 24extending upward at about a forty-five degree angle with the top surfaceof the longitudinal counterbalance 26. The first side of the largeabutment faces toward the second side of the small abutment. A generallyrectangular vibrating screen housing 79 has at least two rows ofdownward extending trapezoidal abutments on a bottom surface thereof.The trapezoidal abutments fixedly connect on a third side to free endsof the upward extending drive coils 20 and on a fourth side to free endsof the upward extending leaf springs. The vibrating screen housing 79has at least one screen and preferably a plurality of screens extendingthe width and length thereof and at least two output apertures formedtherein. The longitudinal counterbalance support base 26 has a pluralityof motors 30 mounted at a front end 15 thereof. The motors have outputshafts extending from top and bottom ends with eccentric weights mountedon the shafts in mechanical time with one another. A programmable motorcontrol unit is capable of driving the motors with the weightssynchronized with one another and capable of driving the motors at aselected speed and of periodically changing the speed for a selectedtime interval by a selected amount.

The present application provides a vibrating screen for separatingdifferent sizes of aggregate in a continuous flow process whereinaggregate flows into a hopper, down onto one end of a vibrating screen,and is transported over the screen by vibration of the screen. Fine andmedium sized portions of the aggregate fall through the first screen toa second screen. Only fine portions fall through the second screen. Thusthe aggregate is separated into three grades of material. The vibratingscreen is rotatably connected to a moveable intermediate base member bya plurality of leaf springs fixedly connected at about a forty-fivedegree angle between the longitudinal counterbalance 26 and thevibrating screen frame unit 9 and a plurality of coil springs called‘drive springs’ 20 which are connected at 45 degrees with the leafsprings between the longitudinal counterbalance and the vibratingscreen. The longitudinal counterbalance in turn is supported above afixed base member by vertical coil springs 22. The longitudinalcounterbalance includes a number of electric motors 30 which haveeccentric weights connected directly to the shafts. When the motors arerunning the spinning eccentric weights cause the vibrating screeningframe 10 to vibrate at a frequency consistent with the speed of themotors. The speed of the motors can be varied to give a differentvibrating frequency.

The mostly horizontal left and right motion of the intermediate basemember therefore causes a left to right and an up and down motion of thevibrating screen housing 79. It can also be seen that, primarily, the‘drive springs’ 20, and to a smaller degree, both the leaf springs 24and the drive springs 20, store and release energy every cycle ofmovement. This system of springs establishes a harmonic system whichtries to maintain a frequency of movement of the system. This storingand releasing of energy allows for a more efficient system with fewerand smaller drive motors for a given throughput of aggregate.

The motors 30 are variable speed and run at one selected speed most ofthe time. Periodically, however, the speed is changed by a selectedamount for a selected period of time and then returned to normal. Thischange in speed dislodges jams or clogs that occasionally occur in theprocess, due to density and particle variance, moisture, and so forth.The vibrating screen of the present invention gives superior performancewhere moist aggregate is an issue.

A programmable motor controller easily accomplishes this periodic cycleof motor speed change. A user can easily change the cleaning cycle timeand amount of speed change, as desired.

The preferred embodiment includes an input hopper 100 with a vibratorymotor 31 to vibrate the provide consistent feed rate of aggregate ontothe vibrating screens. Another preferred embodiment has a hopper withouta separate vibratory drive motor and wherein the gap between the bottomof the hopper is adjusted manually to give an ideal flow of aggregateover the input end of the vibrating screen. This hopper is preferablyfitted with a device which strikes the side of the hopper periodicallyor whenever a bridging or clogging of aggregate is detected.

It is anticipated that a feed box may be used between the hopper and thevibratory screen comprising a short length conveying trough utilized atthe inlet end of the conveyor where the incoming bulk solid needs to bestratified to avoid abrasive wear from impacting and the unnecessaryblinding of the screen medium on its upstream extremity. The feed to thescreening unit needs to be uniform and with a reasonable spread acrossits width.

Referring now to the drawings, the vibration drive isolation system orassembly is arranged to minimize vibration to exterior plant equipment.Vibration drive isolation system includes a longitudinal counterbalancemember 26, a plurality of drive springs 20 supported by longitudinalcounterbalance member 26 and a plurality of isolation springs 22supporting the longitudinal counterbalance member 26. A structural steelbase 4 supports the isolation springs 22. The vibration unit has avariable speed motor control capable for adjusting the vibrationintensity.

Both the time between oscillations and the intensity of the oscillationcan be controlled with an easy control panel adjustment of controller.They require no mechanical adjustment of eccentrics.

The electric motors 30 of the vibratory drive assembly are attached tothe dynamic counter-balance 26 1 and positioned at the front end 15 orunder the combination of the steel coil drive springs 20 and multipleflat bar type of stabilizers. The assembly is supported from thelongitudinal counter-balance 26 by the appropriately spaced isolatingsprings 22 mounted in compression and appropriately spaced along itslength. The vibratory motors with shaft mounted eccentric weights 80 areeither installed on each side of the counter-balance 26 as shown in FIG.7 , or combined together, and placed at the front end 15 of thecounter-balance.

The steel coil type drive springs 20 are distributed across the widthand along the length of the underside of the screen unit 9. The drivesprings 20 are combined with flat bar type stabilizers 24 to assure auniform stroking action. The flat bar type stabilizers 24 are used toguide the movement of the stiff drive springs 20.

The drive springs 20 are sub-resonant tuned to cause them to inherentlywork harder under load, where sub means under and Resonant means naturalfrequency. Therefore, “Sub-resonant” means the maximum running speed ofthe vibratory motors 30 is always under the natural frequency of thecombined drive springs. For example, if the top motor speed is 570 RPM,which in this instance is the same as CPM, then the natural frequency ofall the drive springs 182 would be, for example, 620 CPM. While 570 CPMis preferred, other frequencies such as 720 CPM, 900 CPM or 1200 CPM,might be useful for various applications.

The axial centerline of the steel coil drive springs 20 is provided inline with the wanted stroke angle, but the axial centerline of thestabilizer 24 is perpendicular to the stroke angle. By utilizingparalleled counter-balance 26 as a longitudinal configuration, theenclosed vibrating screening feeder 10 is dynamically counter-balanced.The structural Natural Frequency of the counter-balance assembly will beat least 1.4 times the maximum speed of the motors, but preferably willexceed it. In this instance, the RPM of the motor 30 is the same as thevibrating CPM of the enclosed vibrating screening feeder 10.

Relatively soft steel coil type isolation springs 22 are used to supportthe longitudinal counter-balance 26 which in turn supports the enclosedvibrating screening unit 9 above it. Preferable needed input power isproved by three phase, A-C squirrel cage vibratory motors 30. Electricaladjustment of conveying speed is provided by the controller implementseither as a variable voltage or an adjustable frequency type ofelectrical control. The conveying speed of the ash over the vibratingscreening feeder 10 can be electrically adjusted.

In operation, the vibratory motor(s) 30 are energized and the shaftmounted eccentric weights are accelerated to full speed. The forceoutput of the rotating eccentric weights excites or induces all thestiff steel coil drive springs 20 and flat bar stabilizers 24 to vibrateback and forth in a straight line. The speed (RPM) of the vibratorymotors 30 is the same as the vibrating frequency (CPM) of the drivesprings 20. This happens even though the natural frequency of the drivesprings 20 is above the motor speed. Consequently, the enclosedvibrating screening feeder 10 vibrates at a prescribed amount of linearstroke at the wanted angle, which is usually 45 degrees. As an equalreaction to the vibratory movement of feeder 10, the counter-balancemember 26 inherently moves in an opposite direction. Thus, the opposingdynamic forces cancel one another. The counter-balance 26 freely movesor floats on top the soft isolation springs 22 supporting it.

A resulting directional, straight line stroke on the enclosed unitinduces the particles to unidirectional move forward simultaneously overthe screens and pan. This particle movement is the result of a series ofhops or pitches and catches by the applied vibration. Normally, theparticles first settles on screen. Then, it is gradually moved forwardby repetitive on and off cycles of applied vibration. For example, theparticles are moved 3 feet every 6 minutes. Alternatively, the particlemovement over the screen surfaces could be electrically adjusted viaadjustment of motor operation by controller to provide, for example, aconveying speed of 0.5 FPM. The particles conveyed on the screensdischarges into vertical chutes. The particle sifting that fall throughany openings in the screens drop onto the bottom conveying pan 11. Whenthe vibratory conveying action is applied, these particles move forward.Eventually, these particles fall down through outlets located near thedischarge end of the screening unit 9.

The vibrating screening feeder 10 includes a plurality of vibratorymotors 30 placed relatively close together on the front end 15 of thelongitudinal counterbalance 26. In one embodiment, a total of sixvibratory motors are disposed transversely across from one another withrespect to the longitudinal width of the vibrating screening feeder 10.Each vibratory motor includes a rotatable eccentric weight. Since therotating eccentric weights are located on the top and bottom of eachmotor, a total of twelve individual eccentric weights would be involved,but all of the eccentric weights on a single motor are considered hereinto be a single eccentric weight. The eccentric weight attached to one ofthe vibratory motors in a pair of vibratory motors is substantiallyequal in size to the eccentric weight attached to the other vibratorymotor in the pair of vibratory motors. Each motor is rated 45-60 HP,which would make a total of 270-300 HP provided by the six vibratorymotors although other sizes of motors can be used. While electric motorsare preferred, air motors or hydraulic motors can also be used.

Each vibratory motor preferably has the substantially same sizeeccentric weight attached thereto, such that each vibratory motor andeccentric weight produce substantially the same force output duringoperation.

All six motors synchronize and provide an accumulatively phased forceoutput equal to the sum of the individual force outputs of all of theeccentric weights. The proper phasing of the eccentric weights happensif each pair of motors is started separately, or in any combination, orall started at the same time. These motors would still try to “phase”even if the rotation was different when these six motors are working inconjunction with sub-resonant tuned steel coil drive springs that haveflat bar type stabilizers to guide their stroke line.

The goal is to make the load carrying vibrating screening feeder 10 tovibrate at a prescribed stroke of, for example, one-half inch at afrequency of 570 cycles per minute (CPM), which is the same as therotational speed of the motors at 570 revolutions per minute (RPM). Inother words, the operating frequency of the conveying apparatus 10 inCPM is the same as the RPM of the motors.

After being energized at the same time all six the motors accelerate therotatable eccentric weights installed on the top and bottom shaftextension of the motors. While the weights are accelerating, a slight“shimmy” or shudder-like movement may be present. After all six motorshave reached full speed, the stroke on the conveying trough assemblybegins to grow steadily from, for example, from one-eighth inch to thedesired maximum of one-half inch in about twenty seconds. Thus, thethree pairs of motor combinations require about ten to twenty secondsafter being energized to accelerate the eccentric weights and toproperly “phase” or to accumulatively synchronize the outputs of theeccentric weights.

All of the rotating eccentric weights may have exactly the same forceoutput. If any of these motors is de-energized, then the resultingstroke on the vibrating screening feeder will decrease from its maximumamount.

The “phased” or synchronized eccentric weights on the vibratory motorsexcite or prompt the steel coil drive springs 20 to move back and forth,or compress and extend, in a straight line of stroke. That “line” isguided by the flat bar type stabilizers 24 installed at 90 degrees orperpendicular to the axial centerline of the steel coil drive springs20. The vibratory screening unit 9 positioned on top of the drive springbrackets vibrates back and forth in reaction to the movement of thelongitudinal counterbalance 26 below. This is in keeping with Newton'sLaw of an “equal and opposite reaction”. Stabilization of the drivesprings 20 must be relatively rigid in a direction transverse to theline of stroke and relatively weak in the direction of stroke. Forexample, the flat bar stabilizer 24 may be five inches wide across itstransverse width and only one-eighth inch thick in the direction of thestroke. If the drive springs 20 are not rigidly stabilized in adirection transverse to the line of stroke, then the rotating eccentricweights may not synchronize. The stabilizers 24 may be formed in otherconfigurations than as flat bars so long as the stabilizer is relativelyrigid in a direction transverse to the line of stroke and relativelyweak in the direction of stroke. The vibratory motors are tilted orinclined from horizontal to agree with the stroke line and the installedinclined angle of the drive springs 20.

The entire apparatus vibrates very smoothly and quietly when all sixmotors are up to their full speed. The amount of vibratory strokeremains constant or steady. A given amount of bulk solid, such asfoundry sand, in the vibrating screening feeder installed above thelongitudinal counterbalance 26 can be conveyed forward at a steady speedof, for example, approximately forty feet per minute (FPM).

In another embodiment, the stiff steel coil drive springs 20 have acombined natural frequency that is always above the maximum speed of themotors being utilized. “Sub” means “under” and “resonant” means “naturalfrequency”. Therefore, “sub-resonant” means to maintain the top runningspeed of the motor (for example, 600 RPM or CPM) to always be under the“natural frequency” of all the steel coil drive springs 20 (for example,650 CPM) when the vibratory conveyor 10 is in the “no load” state orempty condition. When a load is applied to the vibrating screeningfeeder the “natural frequency” of all the installed drive springs 20will inherently reduce in response to the added weight of the load (forexample, to 625 CPM). Because the natural frequency of the drive springs20 has decreased (from 650 to 625 CPM), and moved closer to the motorspeed (600 RPM or CPM), the entire drive configuration works harder. Themore the natural frequency of the drive springs decreases because ofadditional load being added to the vibrating screening feeder, the moreclose the natural frequency of all the drive springs 20 comes to therunning speed of the motors. Thus, the drive configuration works evenharder. This is the advantage of “sub-resonant” tuning.

Consequently, the stiff steel coil drive springs 20 in combination withthe six motors inherently drive harder when load is applied to thevibrating screening feeder 10. Therefore, the use of “sub-resonant”tuning takes advantage of the principal of “natural frequency”. However,it should be noted this kind of drive configuration does not normallyoperate in “natural frequency”.

The objective is to make the respective force outputs of the eccentricweights to “pull” the screens of the vibrating screening feeder 10 intension from the discharge end as compared to “pushing” the inertialmass in compression from the inlet end. The same relationship is wantedfrom the total number of drive springs 20 installed that help to makethe apparatus vibrate. This is the reason the collective forces fromboth the rotating eccentric weights and the drive springs should placethe overall length of the vibratory apparatus in tension as compared tobeing in compression. More simply stated, the vibratory apparatus isdynamically being “pulled” instead of being “pushed”.

When an electrical means for adjusting the operating stroke andfrequency of the vibratory machine is wanted, it is preferred to belarge enough to control the total combination of paired motors installedon the vibratory apparatus. To ensure each of those individualcontrollers are responding to the same electrical pilot signal (usually4 to 20 ma D.C.) to ensure each of the motors is rotating at the samespeed throughout the range of adjustment. This maybe accomplished by useof a common electrical potentiometer on either the variable voltage orthe frequency inverter type of electrical controls. The simultaneousadjustment of the operating stroke and frequency by means of a variablevoltage electrical control as outlined in U.S. Pat. Nos. 3,251,457 and4,015,705 can be successfully utilized. As a substitute for the variablevoltage control, a frequency inverter can also be utilized.

Since these motors are combined with sub-resonant tuned drive springs 20that are properly stabilized by stabilizers 24, the plurality of motorsrequires less work output to align with the movement of the stiff drivesprings 20 than it would be to try to be “out of step” or not phased oraccumulatively synchronized with all the sub-resonant tuned drivesprings 20.

The foregoing detailed description is given primarily for clearness ofunderstanding and no unnecessary limitations are to be understoodtherefrom, for modification will become obvious to those skilled in theart upon reading this disclosure and may be made without departing fromthe spirit of the invention and scope of the appended claims.Accordingly, this invention is not intended to be limited by thespecific exemplification presented herein above. Rather, what isintended to be covered is within the spirit and scope of the appendedclaims.

I claim:
 1. A vibrating conveyor screening and feeding process includingthe steps of: providing a bed having an inlet end and an outlet end onwhich material is adapted to be conveyed in a direction, said bed havinga vibrating screen housing including at least one screen in flowcommunication with a pan extending the width and length of said bed;providing a plurality of drive springs, each one of said plurality ofdrive springs having a first end attached to said bed and a second endattached to a longitudinal counterbalance, each one of said plurality ofdrive springs adapted to compress and extend along a line of stroke;providing a plurality of stabilizers, each one of said plurality ofstabilizers having a first end attached to said bed and a second endattached to a longitudinal counterbalance, each one of said plurality ofstabilizers being more rigid in a direction transverse to said line ofstroke than in a direction of said line of stroke; fixedly connectingsaid bed to said plurality of said drive springs and said plurality ofstabilizers at an angle to said longitudinal counterbalance supportingsaid longitudinal counterbalance with a plurality of isolation springsextending upward from a base; providing a plurality of paired vibratorymotors including at least a first vibratory motor having a firstrotatable eccentric weight adapted to rotate about a first axis and asecond vibratory motor having a second rotatable eccentric weightadapted to rotate about a second axis, said first axis being locatedsubstantially in a first plane and said second axis being locatedsubstantially in a second plane, said second plane being non-coplanarwith said first plane, said first axis being spaced apart from saidsecond axis along the direction the material is conveyed, said firstrotatable eccentric weight and said second rotatable eccentric weightare free-wheeling with respect to one another, said first vibratorymotor and said second vibratory motor are adapted to operate atsubstantially the same operating speed and to provide an output forcegenerally perpendicular to its axis of rotation, said first rotatableeccentric weight and said second rotatable eccentric weight are adaptedto accumulatively synchronize with one another without beingrotationally coupled to one another such that the combined resultingoutput force of said first rotatable eccentric weight is parallel to aline of stroke and a combined resulting output force of said secondrotatable eccentric weight; operating said first vibratory motor andsaid second vibratory motor to rotate said first rotatable eccentricweight and said second rotatable eccentric weight, such that said firstrotatable eccentric weight and said second rotatable eccentric weightaccumulatively synchronize and accumulatively add their output forcesand their respective power outputs and thereby vibrate said bed alongsaid line of stroke at a vibration frequency; operating said firstvibratory motor and said second vibratory motor at substantially thesame selected operating speed which approaches being equal to, or isless than, the natural frequency of said plurality of drive springswhich are vibrating said bed; using a programmable motor control unitproviding a standard variable frequency combined with an adjustabletimer creating a vibratory stroke of 50 hertz for 25 seconds and anautomatic momentary pulsing of at lest 60 hertz of from 3 to 5 secondsenabling a full zero to maximum output adjustment.
 2. The vibratingconveyor screening and feeding process of claim 1, including the step ofconveying material on said bed including a vibrating screen housing andat least one screen in flow communication with a pan extending the widthand length of said bed, said vibrating screen housing including aplurality of downward extending abutments on a bottom surface of saidbed fixedly connecting to a plurality of said drive springs mounted atan angle to a longitudinal counterbalance supported by a plurality ofisolation springs extending upward from a base, said longitudinalcounterbalance including said plurality of paired vibratory motorsmounting to a selected end thereof with said plurality of stabilizersextending upward from said longitudinal counterbalance to said downwardextending abutments.
 3. The vibrating conveyor screening and feedingprocess of claim 2, including the step of fixedly connecting said bed tosaid plurality of said drive springs and plurality of stabilizersmounted at an angle to said support which comprises a longitudinalcounterbalance supported by a plurality of isolation springs extendingupward from a base.
 4. The vibrating conveyor screening and feedingprocess of claim 1, including the step of uniformly adjusting thevibration frequency by adjusting the rotational speed of each of saidplurality of paired vibratory motors while operating at substantiallythe same rotational speed with respect to one another.
 5. The vibratingconveyor screening and feeding process of claim 1, including the step ofadjusting a rate of feed by adjusting an operating stroke and afrequency of said plurality of drive springs and said plurality ofstabilizers.
 6. The vibrating conveyor screening and feeding process ofclaim 1, including the step of rotating said first rotatable eccentricweight and said second rotatable eccentric weight in opposite directionsrelative to one another.
 7. The vibrating conveyor screening and feedingprocess of claim 1, including the step of selecting an alternatingcurrent motor for each one of said plurality of paired vibratory motors.8. The vibrating conveyor screening and feeding process of claim 1,including the step of adjusting said plurality of paired vibratorymotors having an output shaft extending from a top end and a bottom endwith an eccentric weights mounted thereon over a complete range of zeroto maximum output.
 9. The vibrating conveyor screening and feedingprocess of claim 1, including the step of controlling a rate of feedmaterial by monitoring the amps pulled by an apparatus being feed bysaid bed and measuring the feedback to increase or decrease the rate ofspeed of said plurality of paired vibratory motors by controlling theamps pulled by said plurality of paired vibratory motors.
 10. Thevibrating conveyor screening and feeding process of claim 1, includingthe step of mounting said plurality of paired vibratory motors to aselected end of said longitudinal counterbalance.
 11. The vibratingconveyor screening and feeding process of claim 1, including the step offixedly connecting said first end of said plurality of drive springs andsaid first end of said plurality of stabilizers at a selected angle to aplurality of downward extending abutments disposed on a bottom surfaceof said bed and mounting said second end of said plurality of drivesprings and said second end of said plurality of stabilizers to saidlongitudinal counterbalance.
 12. The vibrating conveyor screening andfeeding process of claim 8, including the step of mounting an eccentricweight on each of said output shafts extending from a top end and abottom end of said plurality of paired vibratory motors which are inmechanical time with one another.
 13. The vibrating conveyor screeningand feeding process of claim 1, including the step of using saidprogrammable motor control unit to synchronize the speed of saidplurality of paired vibratory motors and periodically changing saidspeed for a selected time interval by a selected amount.
 14. Thevibrating screening and feeding process of claim 1, including the stepof sub-resonant tuning said plurality of drive springs to drive harderunder loaded conditions.
 15. The vibrating screening and feeding processof claim 1, including the step of selecting said plurality of drivesprings and plurality of isolation springs from steel coil springs andselecting said plurality of drive springs which are stiffer than saidplurality of isolation springs.
 16. The vibrating conveyor screening andfeeding process of claim 1, including the step of operating saidplurality of paired vibratory motors at an operating frequency below theresonance point of said drive springs.
 17. The vibrating conveyorscreening and feeding process of claim 1, including the step of usingsaid drive springs for producing a first portion of a load that opposesa vibratory motion and a plurality of said stabilizers for guiding themotion, and said plurality of paired vibratory motors for producing aremaining portion of the load that opposes said vibratory motion. 18.The vibrating conveyor screening and feeding process of claim 1,including the step of operating at a prescribed stroke at a selecteddistance over a selected frequency measured in cycles per minute wherebya rotational speed of said plurality of paired vibratory motors inrevolutions per minute is the same as the operating frequency of saidvibrating conveyor screening feeder.
 19. The vibrating conveyorscreening and feeding process of claim 1, including the step of formingequal acceleration in both directions of a back and forth movement ofsaid vibratory stroke.
 20. A vibrating conveyor screening and feedingprocess including the steps of: providing a bed having an inlet end andan outlet end on which material is adapted to be conveyed in adirection, said bed having a vibrating screen housing including at leastone screen in flow communication with a pan extending the width andlength of said bed; providing a plurality of drive springs, each one ofsaid plurality of drive springs having a first end attached to said bedand a second end attached to a longitudinal counterbalance, each one ofsaid plurality of drive springs adapted to compress and extend along aline of stroke; providing a plurality of stabilizers, each one of saidplurality of stabilizers having a first end attached to said bed and asecond end attached to a longitudinal counterbalance, each one of saidplurality of stabilizers being more rigid in a direction transverse tosaid line of stroke than in a direction of said line of stroke; fixedlyconnecting said bed to said plurality of said drive springs and saidplurality of stabilizers at an angle to said longitudinal counterbalancesupporting said longitudinal counterbalance with a plurality ofisolation springs extending upward from a base; providing a plurality ofpaired vibratory motors including at least a first vibratory motorhaving a first rotatable eccentric weight adapted to rotate about afirst axis and a second vibratory motor having a second rotatableeccentric weight adapted to rotate about a second axis, said first axisbeing located substantially in a first plane and said second axis beinglocated substantially in a second plane, said second plane beingnon-coplanar with said first plane, said first axis being spaced apartfrom said second axis along the direction the material is conveyed, saidfirst rotatable eccentric weight and said second rotatable eccentricweight are free-wheeling with respect to one another, said firstvibratory motor and said second vibratory motor are adapted to operateat substantially the same operating speed and to provide an output forcegenerally perpendicular to its axis of rotation, said first rotatableeccentric weight and said second rotatable eccentric weight are adaptedto accumulatively synchronize with one another without beingrotationally coupled to one another such that the combined resultingoutput force of said first rotatable eccentric weight is parallel to aline of stroke and a combined resulting output force of said secondrotatable eccentric weight; operating said first vibratory motor andsaid second vibratory motor to rotate said first rotatable eccentricweight and said second rotatable eccentric weight, such that said firstrotatable eccentric weight and said second rotatable eccentric weightaccumulatively synchronize and accumulatively add their output forcesand their respective power outputs and thereby vibrate said bed alongsaid line of stroke at a vibration frequency; operating said firstvibratory motor and said second vibratory motor at substantially thesame selected operating speed which approaches being equal to, or isless than, the natural frequency of said plurality of drive springswhich are vibrating said bed; using a programmable motor control unitproviding a standard variable frequency combined with an adjustabletimer creating a vibratory stroke of a selected first hertz rate for aselected first time and an automatic momentary pulsing of at a selectedsecond higher hertz rate for a selected second shorter time enabling afull zero to maximum output adjustment.
 21. The vibrating conveyorscreening and feeding process of claim 20, including the step ofconveying material on said bed including a vibrating screen housing andat least one screen in flow communication with a pan extending the widthand length of said bed, said vibrating screen housing including aplurality of downward extending abutments on a bottom surface of saidbed fixedly connecting to a plurality of said drive springs mounted atan angle to a longitudinal counterbalance supported by a plurality ofisolation springs extending upward from a base, said longitudinalcounterbalance including said plurality of paired vibratory motorsmounting to a selected end thereof with said plurality of stabilizersextending upward from said longitudinal counterbalance to said downwardextending abutments.
 22. The vibrating conveyor screening and feedingprocess of claim 21, including the step of fixedly connecting said bedto said plurality of said drive springs and plurality of stabilizersmounted at an angle to said support which comprises a longitudinalcounterbalance supported by a plurality of isolation springs extendingupward from a base.
 23. The vibrating conveyor screening and feedingprocess of claim 20, including the step of uniformly adjusting thevibration frequency by adjusting the rotational speed of each of saidplurality of paired vibratory motors while operating at substantiallythe same rotational speed with respect to one another.
 24. The vibratingconveyor screening and feeding process of claim 20, including the stepof adjusting a rate of feed by adjusting an operating stroke and afrequency of said plurality of drive springs and said plurality ofstabilizers.
 25. The vibrating conveyor screening and feeding process ofclaim 20, including the step of rotating said first rotatable eccentricweight and said second rotatable eccentric weight in opposite directionsrelative to one another.
 26. The vibrating conveyor screening andfeeding process of claim 20, including the step of selecting analternating current motor for each one of said plurality of pairedvibratory motors.
 27. The vibrating conveyor screening and feedingprocess of claim 20, including the step of adjusting said plurality ofpaired vibratory motors having an output shaft extending from a top endand a bottom end with an eccentric weights mounted thereon over acomplete range of zero to maximum output.
 28. The vibrating conveyorscreening and feeding process of claim 20, including the step ofcontrolling a rate of feed material by monitoring the amps pulled by anapparatus being feed by said bed and measuring the feedback to increaseor decrease the rate of speed by controlling the amps pulled by saidplurality of paired vibratory motors.
 29. The vibrating conveyorscreening and feeding process of claim 22, including the step ofmounting said plurality of vibratory motors to a selected end of saidlongitudinal counterbalance.
 30. The vibrating conveyor screening andfeeding process of claim 21, including the step of fixedly connectingsaid first end of said plurality of drive springs and said first end ofsaid plurality of stabilizers at a selected angle to a plurality ofdownward extending abutments disposed on a bottom surface of said bedand mounting said second end of said plurality of drive springs and saidsecond end of said plurality of stabilizers to said longitudinalcounterbalance.
 31. The vibrating conveyor screening and feeding processof claim 27, including the step of mounting an eccentric weight on eachof said output shafts extending from a top end and a bottom end of saidplurality of paired vibratory motors which are in mechanical time withone another.
 32. The vibrating conveyor screening and feeding process ofclaim 20, including the step of using said programmable motor controlunit to synchronize the speed of said plurality of paired vibratorymotors and periodically changing said speed for a selected time intervalby a selected amount.
 33. The vibrating conveyor screening and feedingprocess of claim 20, including the step of sub-resonant tuning saidplurality of drive springs to drive harder under loaded conditions. 34.The vibrating conveyor screening and feeding process of claim 21,including the step of selecting said plurality of drive springs andplurality of isolation springs from steel coil springs and selectingsaid plurality of drive springs which are stiffer than said plurality ofisolation springs.
 35. The vibrating conveyor screening and feedingprocess of claim 20, including the step of operating said plurality ofpaired vibratory motors at an operating frequency below the resonancepoint of said drive springs.
 36. The vibrating conveyor screening andfeeding process of claim 20, including the step of using said drivesprings for producing a first portion of a load that opposes a vibratorymotion and a plurality of said stabilizers for guiding the motion, andsaid plurality of paired vibratory motors for producing a remainingportion of the load that opposes said vibratory motion.
 37. Thevibrating conveyor screening and feeding process of claim 20, includingthe step of operating at a prescribed stroke at a selected distance overa selected frequency measured in cycles per minute whereby a rotationalspeed of said plurality of paired vibratory motors in revolutions perminute is the same as said selected frequency.
 38. The vibratingconveyor screening and feeding process of claim 20, including the stepof forming equal acceleration in both directions of a back and forthmovement of said vibratory stroke.
 39. The vibrating conveyor screeningand feeding process of claim 20, wherein said selected first hertz rateis 50 hertz, said selected first time is 25 seconds, said selectedsecond higher hertz rate is at least 60 hertz, and said selected secondshorter time is from 3 to 5 seconds.